|The 1930 OEC record-breaker re-purposed with a supercharged Austin 7 engine|
The Aug. 30, 1934 edition of 'The Motor Cycle' has a short article on a 'A New Racing "Four"', detailing the attempts by J. Granville Grenfell (what a name!) to create a 500cc machine, with the specific intention of being the first motorcycle to achieve 100mph for an hour, and win a 'Motor Cycle' sponsored trophy for a multi-cylinder/100mph/1hour British motorcycle. While the OEC was being built, a New Imperial 500cc v-twin took the prize with 'Ginger' Wood the brave rider - it was said he was the only person willing to risk his life aboard the evil-handling New Imp, which spat him off with a tank-slapper at 100mph on the Brooklands banking, while practicing for the record. By comparison, the OEC was a far safer bet at over 100mph; the 'Duplex' steering system being almost too stable at speed, taking some effort to deflect from a straight-line course. Of the two possibilities, I'd take stable over wobble.
|A closeup of the Austin engine and blower, with a single Amac track-racing carb feeding the sleeved-down 500cc engine|
More technical points on the modified engine: the Centric blower began puffing at 25rpm, giving maximum pressure of 20lbs/sq" at 6000rpm, producing an estimated 46hp 7000rpm...about twice the safe revs of the standard Austin engine, and nearly 3 times the original 17hp. A sporting Watmough cylinder head gave a better combustion chamber shape, although the compression ratio remained a lowly 4.5:1...not an issue with a supercharger, which needs neither high compression nor radical valve timing to produce maximum power. In fact, a very tame camshaft with little 'overlap' of valve openings produces the best results with a blower, as it's the job of the compressor is fill the cylinder completely with fuel/air mix, no fancy engine tuning is required, other than the ability to hold the engine bits together, after a dramatic increase in horsepower.
|The Centric supercharger as used in the OEC-Austin|
Of course, the OEC wasn't the only motorcycle using an 'Austin 7' engine, as Brough Superior used the engine as well - see the Road Test here.
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